Articulated equipment position control system and method

ABSTRACT

An articulated equipment position control system and method are provided for equipment consisting of motive and working components. The components are connected by an articulated connector, such as a pivotal hitch. GPS-derived positional data is utilized for power-articulating the hitch to maintain the working component, such as an implement, on a predetermined course. Operator-induced course deviations can thus be corrected. The working component can also be positioned to follow the course of the motive component. The system includes a microprocessor control subsystem, which interfaces with a steering guidance system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application No.60/432,719, filed Dec. 11, 2002, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to articulated equipmentposition control, and particularly to a system and method for DGPS-basedpositioning of an operative piece of equipment, such as a farmimplement, which is pulled, pushed or carried by a motive piece ofequipment, such as a tractor, by manipulation of a power-articulatedconnection therebetween.

2. Description of the Related Art

Various equipment systems include articulated components. For example, acommon configuration involves a “motive” component, which supplies themotive force for pulling, pushing or carrying a “working” componentthrough an articulated connection located therebetween. For example,tractors serve as motive components in agricultural and otheroperations. The working components can comprise various implements,which perform specific “working” functions.

Articulated connections can be provided between such components toaccommodate relative movement therebetween. For example, detachablehitches allow the equipment systems to be reconfigured in variouscombinations, depending on the task at hand. Moreover, such articulatedinterconnections commonly accommodate relative movement between thecomponents. Common examples in agricultural equipment systems includethree-point hitches, clevis-type hitches, drawbars, etc. “Free” movementarticulated connections include pivotal hitches. “Fixed” articulatedconnections include two-point and three-point hitches. Both types ofarticulated connections allow relative movement between the motive andworking components. Such relative movement may be necessary toaccommodate turning, as in the case of tractors pulling wheeledground-working implements along curved travel paths, which areaccommodated by pivotal hitches. Relative movement in the case oftwo-point and three-point hitches can involve adjusting implementheight, pitch and other attitudes with respect to a tractor.

An example of articulated equipment with GPS-based guidance capabilitiesis shown in U.S. Pat. No. 6,539,303 for GPS Derived Swathing GuidanceSystem, which is incorporated herein by reference. GPS guidance canutilize absolute positioning techniques based on GPS coordinates, orrelative positioning based on previous travel paths and previouslyidentified locations. Various error correction techniques are employedto improve the accuracy of GPS positioning. For example, Whitehead U.S.Pat. No. 6,397,147 for Relative GPS Positioning Using a Single GPSReceiver with Internally Generated Differential Correction Terms and U.SPat. No. 6,469,663 for Method and System for GPS and WAAS Carrier PhaseMeasurements for Relative Positioning are assigned to CSI Wireless Inc.and are incorporated herein by reference. This technology is availablefrom CSI Wireless Inc. under its trademark “e-Dif™”. The GlobalNavigation Satellite System (“GNSS”) currently includes GPS, the GLONASS(“GLObal NAvigation Satellite System”) satellites of the former USSR andother satellite ranging technologies. Current GNSS augmentation systemsinclude WAAS (Wide Area Augmentation System) in the United States, EGNOS(European Geostationary Navigation Overlay System) in Europe and MSAS(Multifunctional Transport Satellite Space-based Augmentation System) inJapan. Each of these augmentation systems, which are all compatible,includes a ground network for observing the GPS constellation, and oneor more geostationary satellites.

Relatively precise GPS positioning can be achieved with real timekinetic (“RTK”) technology. For example, U.S. Pat. No. 6,469,663 forMethod and System for GPS and WAAS Carrier Phase Measurements forRelative Positioning discloses a single frequency RTK solution, and isincorporated herein by reference. Such greater precision cansignificantly expand the commercial applications for DGPS-basedpositioning and navigation. For example, in row crop agriculture,sub-meter tolerances are necessary to avoid equipment damage to crops.The application of DGPS-based automatic guidance offers the potentialfor reducing steering deviation associated with manual steering andguidance based on disk markers, foam markers and other prior art,non-automated techniques. However, guiding articulated agriculturalequipment is particularly challenging because crop damage can be causedby either the motive or the working component, or both.

The present invention addresses this problem by providing a system andmethod for positioning a working component relative to a motivecomponent by a power-articulation of the hitch or other connectiontherebetween. Heretofore there has not been available an articulatedequipment position control system and method with the advantages andfeatures of the present invention.

Other related art patents include: U.S. Pat. No. 6,434,462 for GPSControl of a Tractor-Towed Implement; U.S. Pat. Nos. 5,511,623 and5,664,632 for Quick Hitch Guidance Device; and U.S. Pat. No. 5,725,230for Self Steering Tandem Hitch.

SUMMARY OF THE INVENTION

In the practice of the present invention, a system and method areprovided for controlling the position of an articulated connectionbetween motive and working components in an equipment system. The motivecomponent can comprise a tractor or other piece of equipment, which isdesigned to pull, push or otherwise transport a working component, suchas a ground-working implement, in an articulated equipment system.Control can be based on GPS positional data, and various types of DGPS(Differential GPS) controls can be used, including WAAS and othersuitable error-correction functionalities. A relatively simpleconfiguration with a single DGPS antenna solution can be used. Thisgives the operator guidance as well as providing a correction referencefor the implement position. The system includes a DGPS receiver, whichis preferably mounted on the motive vehicle. A control subsystemincludes an on-board computer, which receives positional data from theDGPS receiver, processes same along with various other input data, andoutputs signals that control the working component position through thearticulated interconnection. The system and method have severaloperating modes, including “Follow GPS/Guidance” whereby the connectionmaintains the position of the implement on a predetermined travel path.In a “Follow/Match Tracks” mode the articulated connection conforms thetravel path of the implement to that of the motive component. A “Manual”operating mode is provided for direct operator control. Bothstraight-line and contour travel paths can be accommodated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of articulated equipment with a DGPS-basedposition control system embodying the present invention.

FIG. 2 is a schematic diagram of the position control system applied toagricultural equipment comprising a tractor and an implement with apower-articulated pivotal hitch.

FIG. 3 is a communication diagram of the position control system shownin FIG. 2.

FIG. 3A is a block diagram of the major components of the positioncontrol system, showing interrelationships therebetween.

FIG. 4 is a front elevational view of an operator interface includingthe input and output devices for controlling and displaying theoperation of the system.

FIG. 5 is a top plan view of the tractor-and-implement system, shownwith the articulated hitch correcting the implement position in responseto a cross-slope field condition with the system in a Follow/MatchTracks, straight-line operating mode.

FIG. 6 is an enlarged, fragmentary top plan view thereof.

FIG. 7 is a top plan view of the tractor-and-implement system, shownwith the articulated hitch correcting the implement position through aturn on a slope in a Follow/Match Tracks, contour operating mode.

FIG. 7A is a top plan view of the tractor-and-implement system, shownwith the articulated hitch correcting a steering deviation cross-trackerror with the system in a Follow GPS/Guidance, straight-line operatingmode.

FIG. 8 shows the operation of the system in a Follow DGPS/Guidance mode.

FIG. 9 shows the operation of the system in a Follow/Match Tracks mode.

FIG. 10 shows the operation of the system in an End Turn procedure.

FIG. 10A is a table showing a Setup: Hitch Calibrate menu.

FIG. 11 is a block diagram of a DGPS-based position control system forarticulated equipment, which system comprises a first modifiedembodiment of the present invention with first and second DGPSreceivers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Introduction and Environment

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

Certain terminology will be used in the following description forconvenience in reference only and will not be limiting. For example, up,down, front, back, right and left refer to the invention as oriented inthe view being referred to. The words “inwardly” and “outwardly” referto directions toward and away from, respectively, the geometric centerof the embodiment being described and designated parts thereof. Saidterminology will include the words specifically mentioned, derivativesthereof and words of similar meaning.

II. Preferred Embodiment Articulated Equipment System 2

Referring to the drawings in more detail, the reference numeral 2generally designates an articulated equipment position control systemembodying the present invention. Without limitation on the generality ofuseful applications of the control system 2, equipment 4 comprising amotive component 6 connected to a working component 8 through anarticulated connection or hitch 10 is shown. Without limitation on thegenerality of articulated connections that can be utilized with thepresent invention, the hitch 10 can comprise, for example, an AdjustableDraw Bar Offset as shown and described in the Miller U.S. Pat. No.6,631,916, which is incorporated herein by reference. Such a hitch isavailable as an Outback Hitch product of RHS, Inc. of Hiawatha, Kans.Also by way of example, the motive component 6 can comprise a tractorand the working component 8 can comprise a ground-working implement.However, the position control system 2 can be applied to other equipmentconfigurations for a wide range of other applications. Such applicationsinclude equipment and components used in road construction, roadmaintenance, earthworking, mining, transportation, industry,manufacturing, etc.

III. Control Subsystem 12

The power-articulated connection 10 enables positioning the workingcomponent 8 from the motive component 6 by means of a control subsystem12. The control subsystem 12 is associated with and mounted in themotive component 6, for example, inside the tractor cab thereof. Thecontrol subsystem 12 includes a microprocessor 14 which receives inputsignals from a DGPS receiver 16 connected to an antenna 18, which can bemounted on the roof of the tractor cab. The microprocessor 14 processesand stores the differentially corrected positional data received throughthe DGPS receiver 16.

FIG. 2 shows an exemplary configuration of the control subsystem 12 witha steering guide 20, which can comprise an Outback S steering guideavailable from RHS, Inc. of Hiawatha, Kans. and manufactured by CSIWireless Inc. of Calgary, Canada. The Outback S steering guide isdescribed in U.S. Pat. No. 6,539,303 for GPS Derived Swathing GuidanceSystem, which is incorporated herein by reference. The steering guide 20includes a steering display 21 with an arcuate array of steeringindicator lights for guiding an operator along a travel path. Anoptional field mapping device 23 can be connected to the steering guide20 by a CAN cable 25. The field mapping device 23 can comprise, forexample, an Outback 360 device available from RHS, Inc. of Hiawatha,Kans. and manufactured by CSI Wireless Inc. of Calgary, Canada. A hitchposition control device 27 is connected to the steering guide 20 throughthe CAN cable 25 and includes an arcuate hitch position display 42 withmultiple indicator lights 44 (FIG. 4), as described in more detailbelow. The output devices connected to the control subsystem 12 includesolenoid-controlled valves 22 for operating piston-and-cylinder units24, which are operably connected to the hitch 10 and to an hydraulicfluid pressure source 62. The hitch 10 includes a pivotable draw bar 11with a hitch pin 30 mounted at its trailing end for connecting theworking component 8.

FIG. 3 is a communication diagram for the position control system 2.FIG. 3A is a block diagram showing the major components of the system 2and some of the types of data and control signals, which are transmittedamong the system components in operation.

A hitch position control input/output (“I/O”) user interface 26 includesa hitch guidance control panel 28 (FIG. 4). The control panel 28includes indicators for “Follow GPS” mode 34, “Match Tracks” mode 36 and“Manual” mode 38. A mode selector switch 40 is provided for sequentiallycycling through the operating modes, as indicated by the indicators 34,36 and 38.

A downwardly-concave, arcuate hitch position indicator light array 42comprises multiple left side (port) indicator lights 43, a centerindicator light 44 and multiple right side (starboard) indicator lights45. The lights 43, 45 can be color-coded (e.g., left=red and right=green). The amount of lateral hitch swing or deflection isproportionally indicated by the number of lights 43, 45 illuminated oneither side of the center light 44. The control panel 28 includes leftand right switches 46 a,b respectively, which are used for swinging theimplement 8 left and right respectively. A “RUN” switch 48 is providedfor initiating operation of the control subsystem 12. A “HOLD” switch 50effectively pauses the control software. A “CENTER” switch 52 centersthe hitch 10. The “S Present” indicator light 54 indicates the operationof the steering guide 20, e.g. an “Outback S™” system.

Additional input to the control subsystem 12 is provided by apotentiometer 56 associated with a respective piston-and-cylinder unit24 for indicating the extended/retracted condition thereof. Thecross-track, curvature and tilt inputs are calibrated relative to thevalve potentiometer 56 position. A tilt sensor 58 is mounted on thehitch 10 for indicating a tilt angle of the equipment 4, which inputdata are utilized in correcting for sloping field conditions.

IV. Operation

In one exemplary application of the system 2, a clevis-type, pivotalhitch 10 is power-articulated to adjust the position of a workingimplement 8 with respect to a tractor 6. A “Towed Point” at the hitchpin 30 is adjusted mechanically based on and in response to inputs,which can include: GPS-derived signals indicating cross-track error(i.e., steering error representing displacement from the desired track32 (FIG. 7A)); GPS-derived speed; GPS-derived heading; and tilt asdetected by the tilt sensor 58.

The system 2 has three modes of operation: Follow GPS/Guidance,Follow/Match Tracks and Manual.

1. Follow GPS/Guidance Mode (FIGS. 7A and 8). The system 2 correctsoperator errors and course deviations by positioning the implement 8 onthe desired track. Operation is in either straight mode (sometimesreferred to as point A-to-point B or A-B guidance), where straight linesare followed (FIG. 7A), or contour mode (FIG. 8), where guidance isagainst a previously driven pass. Driver error is corrected throughcompensation by the hitch position on the towing vehicle 6 so that theworking implement 8, and equipment thereon, are better positioned, whichminimizes overlap and missed areas. In guidance mode, positionalcross-track steering error information is provided by the steering guide20, which can assist the operator in maintaining the tractor 6 on adesired travel path. Operator deviations from the desired travel pathare accommodated by the control system 2, whereby the implement 8 ismaintained on course, regardless of operator-based errors and coursedeviations. The corrected travel path data are input to the controlsubsystem 12 based on actual hitch pin 30 positions. Therefore, thesystem 2 is able to accurately track and record the travel path of theimplement 8, regardless of the tractor 6 course deviations. Hitchposition (hitch line) is calculated relative to the cab antenna 18position. The hitch automatically maintains the hitch pin 30, andtherefore the implement 8, on the desired track 32, compensating fortractor steering deviations (FIG. 7A).

In Follow GPS/Guidance mode, the cross-track error of the GPS steeringguide 20, which is typically mounted on the tractor 6, from the presentposition to the desired track is used as the feedback element for thesystem. The guidance mode can be either straight (FIG. 7A) or contourmode. The cross-track error is thus used to power-articulate the hitch10 to move it a corresponding amount up to its maximum travel. Forexample, if the DGPS navigation system 12 shows that the tractor 6 issix inches to the left of the GPS guideline or desired track 32, thehitch 10 will be moved six inches to the right, thus placing the hitchpin 30 approximately over the desired track 32 (FIG. 7A). Using the GPSpositioning data from the steering guide 20 and the hitch positionsignals from the potentiometer 56 through the hitch control 27, thehitch pin 30 position is maintained generally over the GPS guideline ordesired track 32. The towed implement 8 is thus placed in the correctposition. The system 2 functions in this manner in both straight-lineand contour submodes of the Follow GPS/Guidance operating mode.

2. Follow/Match Tracks Mode (FIGS. 5–7 and 9). In this mode the system 2corrects for curvature and slope by positioning the trailer or implement8 to follow in the tracks of the tractor 6. Otherwise the implementcould slip down-slope and/or shortcut turns and cause damage by runningover the crop rows. With the system 2 in Follow/Match Tracks operatingmode, the hitch 10 is adjusted to compensate for tilting and curvatureeffects on the equipment 4. Such effects are encountered in fields withsloping and/or contour (i.e. curved travel path) conditions. The wheelsof the pulled implement 8 will thus follow in the tracks of the tractor6 in order to minimize crop damage.

With “Follow Tracks” mode selected on the control panel (FIG. 4), thetilt sensor 58 outputs a slope value. The system 2 will compensate forthe slippage by moving the hitch 10 up-slope (FIGS. 5 and 6). Dependingon load and soil conditions, this compensation value is variable and canbe adjusted on-the-fly with the left and right arrow switches 46 a and46 b respectively.

At least five conditions are possible: a) straight/level, therefore nocorrection; b) straight/side slope, therefore correction for onevariable; c) turn/level, therefore correction for one variable; d)turn/downhill, therefore correction for two variables; and e)turn/uphill (FIG. 7), therefore correction for two variables.

3. Manual Mode. In this mode the operator can manually controlarticulation of the hitch 10 through the left/right switches 46 a/46 b.The hitch 10 can be centered with the center switch 52 (FIG. 4).

FIG. 10 shows an automatic turnaround detection feature, which isactivated when the hitch 10 deviates more than a predetermined distance,such as two meters, from the guideline. It automatically swings thehitch 10 to a far outside-of-turn position. At the end of each pass, thecontrol subsystem 12 detects such a deviation from a predeterminedguidepath, or desired track 32, whereupon the system 2 enters anend-of-turn procedure to facilitate tightly turning the equipment 4.Such turns are typically “keyhole” turns. The implement is first turnedin one direction and the hitch 10 is shifted to the outside of thatdirection, whereafter the operator turns the equipment in the otherdirection through more than 180 degrees with the hitch 10 shifted to theoutside of that turn, followed by a final turn with the hitch 10shifting to the outside of the final turn. This feature avoids conflictbetween the components 6, 8 during tight turns, such as those which maybe encountered at the ends of passes. At the end of each row when thevehicle is turning the operator typically carries out what is called akeyhole turn. This allows the vehicle and trailer to be turned in aminimal distance. In either Follow GPS/Guidance mode or Follow/MatchTracks mode, an automatic feature, without user intervention, is thatcurvature correction moves the hitch to the outside of the turn. Thisaids in the tightness of the turn achievable by a tractor and trailer bykeeping the trailer away from the inside wheels. When the system 2deviates from the desired track 32 by more than a predetermined distance(e.g., about two meters), the end-of-turn procedure described above isautomatically initiated. Thus, the operator can concentrate oncompleting the turn while the system 2 automatically positions the hitch10 most advantageously. Automatic return to normal operation occursafter the turn is complete.

A technique to generate an accurate radius of curvature has beendeveloped from the DGPS (Differential Global Positioning System) headinginformation. This value has been found to be proportional to the amountof hitch position movement required to make the implement 8 wheelsfollow those of the tractor 6. Similarly, a tilt sensor input ismeasured and calibrated to maintain the implement wheels in the tracksof the tractor wheels. The microprocessor 14 generates the requiredsignals to activate the piston-and-cylinder unit hydraulic valves 22whereby the hitch 10 accomplishes the required corrections.

Curvature correction is calculated from the GPS information. Heading andspeed are input whereby the system automatically generates the requiredradius of curvature. Using the heading information, typically generatedat a rate of 5 Hz, the rate of heading change, can be calculated indegrees per second. A best fit algorithm of heading and time is used toreduce noise and generate a more stable rate of turn. By knowing theground speed of the vehicle, the radius of curvature of any turn iscalculable with the GPS positioning data inputs. With rate of turn ROTin degrees per second and speed S in meters per second, the radius ofcurvature R in meters can be generated from the formula:R=S*180/(pi*ROT)The line of travel that the hitch 10 has to travel in order to allow thetrailer tires to follow in line with those of the tractor is inverselyproportional to this radius of curvature value. The tighter the turn themore compensation is required up to the limit of the hitch movement.This proportional relationship is generally consistent for similartractor/trailer configurations.V. Calibration Process

FIG. 10A shows a menu for calibrating the system 2 in a setup procedure.The menu appears on the steering display 21, which is part of thesteering guide 20. Operator inputs are made via the steering guide 20and the hitch guidance control panel 28 (FIG. 4). Position adjustment isaccomplished by moving the hitch pin to its far left position with theleft arrow switch 46 a, then ENTER; moving the hitch pin to its farright position with the right arrow switch 46 b, then ENTER; andcentering the hitch with the CENTER switch 52, then ENTER. Curvatureadjustment is accomplished by driving around a curve on relatively flatground while observing the trailing implement tracking. The left andright arrow switches 46 a and 46 b respectively can be used to positionthe implement for accurate “Match Tracks” positioning. The curvaturecompensation value is then updated by pressing ENTER. Slope calibrationis accomplished by placing the tractor 6 on level ground with the slopefunction “ON”, then ENTER to update the level reference value.

VI. Error Correction

(D)GPS errors can be: a) corrected as necessary using existingerror-correction techniques, such as government-sponsored WAAS andEGNOS, commercially available differential services such as thosesupplied by OmniStar and RACAL, e-Dif differential techniques, and bothlocal and wide area RTK methods.

Improved positioning can be achieved by using two DGPS receivers, withantennas mounted on the tractor for operator guidance and on theimplement for implement control, as discussed below.

VII. First Modified Embodiment Dual-Receiver System 102

FIG. 11 shows articulated equipment 104 with a position control system102 comprising a first modified embodiment of the present invention. Thesystem 102 includes first and second DGPS receivers 110, 112 mounted onmotive and working components 106, 108 respectively. This configurationcan be used for automatic steering of the motive component 6 using thefirst DGPS receiver 110 and fine positioning of the working component(implement) 8 using the second DGPS receiver 112.

It is to be understood that the invention can be embodied in variousforms, and is not to be limited to the examples discussed above. Othercomponents can be utilized. For example, the working component cancomprise a sprayer with spray booms connected to a vehicle and adaptedto be raised and lowered in response to GPS position data.

1. A position control system for positioning a working componentrelative to a motive component, which comprises: an articulatedconnection between said components; a locating device associated withsaid motive component and adapted for providing an output correspondingthereto; a controller connected to said locating device and adapted forproviding an output for positioning said components relative to eachother; and a positioning device connected to said controller and atleast one of said components and adapted for positioning said onecomponent relative to the other in response to said controller output;said locating device comprising a first locating device and including aDGPS receiver adapted for providing GPS output corresponding to theposition of said motive component; a second locating device associatedwith said working component and adapted for providing an outputcorresponding thereto; the output of said second locating devicelocating said working component in relation to said motive component;and said positioning device being operably and drivingly connected tosaid working component.
 2. The system of claim 1, which includes: saidcontroller being adapted to stare DGPS-based straight and curved desiredtracks, and providing position-correcting output to said positioningdevice in response to deviations of said motive component from a desiredtrack.
 3. The system of claim 2, which includes: said articulatedconnection comprising a power-actuated hitch including alaterally-movable drawbar and a hitch pin mounted thereon and connectedto said working component; said positioning device including said hitch;and said controller being preprogrammed to laterally shift said hitch inresponse to deviations of said motive component from a respectivedesired track whereby said hitch is adapted to generally follow saiddesired track.
 4. The system of claim 3, which includes: a tilt sensormounted on one of said components and providing an output correspondingto a tilt condition thereof; said system being preprogrammed with atilt-correcting function adapted to proportionally, laterally shift saidhitch in response to a detected tilt condition and a requiredcompensating adjustment; and said system being preprogrammed with acurvature-correcting function adapted to proportionally, laterally shiftsaid hitch in response to a detected curvature of said vehicle track anda required compensating adjustment of said working component track. 5.The system of claim 4 wherein said system is adapted for calibratingsaid tilt-correcting and curvature-correcting functions in either orboth of a stationary and an on-the-fly condition of said system.
 6. Thesystem of claim 3, which includes an end-of-row turn compensatingfunction adapted for biasing said hitch laterally outwardly in responseto said system detecting an end-of-row condition corresponding to apredetermined cross-track deviation from a desired track.
 7. The systemof claim 3, which includes: a steering guide subsystem including asteering display providing cross-track error and heading information toan operator; and said steering guide subsystem being connected to saidcontroller whereby said steering display information is based on GPSdata.
 8. The system of claim 3, which includes: an automatic steeringsubsystem connected to said motive component and to said controller,said automatic steering subsystem being adapted to automatically guidesaid motive component along a desired track.
 9. The system of claim 3,which includes: said hitch having a clevis configuration; said drawbarhaving a front end pivotably connected to said motive component and atrailing end connected to said working component; an hydraulic subsystemincluding an hydraulic pressure source associated with said motivecomponent, an hydraulic actuator connected to said hydraulic pressuresource and to said drawbar for pivoting same and an hydraulic valveselectively controlling pressurized hydraulic fluid flow from saidpressure source to said hydraulic actuator; said controller beingconnected to said hydraulic valve and adapted for controlling theoperation of same; said hitch including an hydraulic piston-and-cylinderunit connected to said hydraulic power source and to said drawbar, saidpiston-and-cylinder unit being adapted for pivoting said drawbar; andsaid second locating device including a potentiometer connected to saidpiston-and-cylinder unit and adapted for providing an output signalproportional to a position of said piston-and-cylinder unit andcorresponding to the orientation of said hitch.
 10. The system of claim9, which includes: a lateral hitch position control input adapted forbiasing said drawbar left and right; and a hitch centering control inputadapted for centering said drawbar on said hitch; and said left, rightand center positions of said drawbar causing said potentiometer toprovide corresponding output to said controller for controlling saidpositioning device.
 11. The system of claim 2, which includes: astraight line operating mode adapted for guiding said implement along arelatively straight-line track; and a contour operating mode adapted forguiding said implement along a curvilinear track.
 12. The system ofclaim 4 wherein said compensating adjustment comprises a turning radiicompensation based on motive component speed and rate-of-turn.
 13. Thesystem of claim 2, which includes DGPS correction capability utilizing asignal correction system from among the group consisting of: WAAS (WideArea Augmentation System), EGNOS (European Geostationary NavigationOverlay System) and MSAS (Multifunctional Transport SatelliteSpace-based Augmentation System).
 14. The system of claim 3, whichincludes: a display device including an arcuate array of indicatorlights adapted for displaying an approximate real-time position of saidworking component relative to a desired track thereof; said indicatorlight array of having a generally downwardly convex configuration with acenter light indicating a hitch position approximately over said desiredtrack and cross-track error of said working component position beingproportionally indicated by corresponding multiples of indicator lightsto each side of said center light; and said controller being connectedto said display device whereby said display device receives workingcomponent position output from said controller and displaysrepresentations of said implement position in response thereto.
 15. Thesystem of claim 10 wherein said controller is adapted for calibrationrelative to said valve potentiometer.
 16. The system according to claim15 wherein said controller calibration is relative to one or more of thefactors comprising cross-track error, guidepath curvature and motivecomponent tilt.
 17. A position control system for positioning a workingcomponent relative to a motive component, which comprises: anarticulated connection between said components comprising apower-actuated hitch including a laterally-movable drawbar and a hitchpin mounted thereon and connected to said working component, said hitchhaving a clevis configuration; said drawbar having a front end pivotablyconnected to said motive component and a trailing end connected to saidworking component by said hitch pin; an hydraulic subsystem including anhydraulic pressure source associated with said motive component, anhydraulic actuator connected to said hydraulic pressure source and tosaid drawbar for pivoting same and an hydraulic valve selectivelycontrolling pressurized hydraulic fluid flow from said pressure sourceto said hydraulic actuator; said controller being connected to saidhydraulic valve and adapted for controlling the operation of same; saidhitch including an hydraulic piston-and-cylinder unit connected to saidhydraulic power source and to said drawbar, said piston-and-cylinderunit being adapted for pivoting said drawbar; a first locating deviceassociated with said motive component and including a DGPS receiveradapted for providing GPS output corresponding to the position of saidmotive component; a second locating device associated with said workingcomponent and adapted for providing an output corresponding thereto, theoutput of said second locating device locating said working component inrelation to said motive component; said second locating device includinga potentiometer connected to said piston-and-cylinder unit and adaptedfor providing an output signal proportional to a position of saidpiston-and-cylinder unit and corresponding to the orientation of saidhitch drawbar; a controller connected to said locating devices andincluding an output for positioning said components relative to eachother; said controller being adapted to store DGPS-based straight-lineand contour desired tracks, and providing position-correcting output tosaid positioning device in response to deviations of said motivecomponent from a desired track; said controller being preprogrammed tolaterally shift said hitch in response to deviations of said motivecomponent from a respective desired track whereby said hitch is adaptedto generally follow said desired track; a tilt sensor mounted on one ofsaid components and providing an output corresponding to a tiltcondition thereof; said system being preprogrammed with atilt-correcting function adapted to proportionally, laterally shift saidhitch in response to a detected tilt condition and a requiredcompensating adjustment; said system being preprogrammed with acurvature-correcting function adapted to proportionally, laterally shiftsaid hitch in response to a detected curvature of said vehicle track anda required compensating adjustment of said working component track; anda display device connected to said controller and adapted to receiveworking component position output therefrom and display representationsof said implement position in response thereto.
 18. A method ofpositioning a working component relative to a motive component, whichmethod comprises the steps of: providing an articulated connectionbetween said components; providing a controller; providing a firstlocating device including a DGPS receiver adapted for providing GPSoutput corresponding to the position of the motive component; generatinga signal corresponding to said motive component position and inputtingsame to said controller; providing a second locating device associatedwith said working component and adapted for providing an output saidcontroller, said output corresponding to the position of said workingcomponent; locating said working component in relation to said motivecomponent with the output of said second locating device; operably anddriving connecting said positioning device to said working component;and positioning said working component relative to said motive componentwith said positioning device in response to said controller.
 19. Themethod of claim 18, which includes the additional steps of: establishinga desired straight-line or contour track for said motive component;guiding said motive component generally along said desired track;determining motive component deviation from said desired track; andpositioning said working component with respect to said desired track inresponse to said deviation.
 20. The method of claim 19, which includesthe additional steps of: defining said desired track and said motivecomponent deviation therefrom with GPS coordinates; inputting said GPScoordinates to said controller; and comparing said desired track anddeviation GPS coordinates.
 21. The method of claim 20, which includesthe additional steps of: generating a radius of curvature through acontour track of said motive component; smoothing said radius ofcurvature; and positioning said working component with respect to saidsmoothed radius of curvature.
 22. The method of claim 20, which includesthe additional steps of: providing a Follow GPS/Guidance operating modeof said controller; compensating for motive component deviation fromsaid desired track; and positioning said working component on saiddesired track.
 23. The method of claim 20, which includes additionalsteps of: providing a Follow/Match Tracks operating mode of saidcontroller; generating a tilt signal corresponding to a tilt of saidsystem and inputting same to said controller; generating a curvecompensation as a function of system speed and course change; andpositioning said working component on said motive component track inresponse to said tilt signal and said curve compensation.
 24. The methodof claim 20, which includes additional steps of: detecting an end-of-rowlocation of said system; turning said system around at said end-of-rowlocation; and biasing said working component to the outside of saidend-of-row turn.